Is there ever a moment in the play where you would consider Black & White as becoming “friends?” If so, where in the play? If not, how would you classify their relationship?

No, I would not consider this a friendship, as the two men know nothing about each other except for the experience at hand. What we have is White... the fallen man, and Black... a caring man who does not hessitate to act. Black stops White from embarking on a senseless death, and in turn, we might see him as not only caring, but as a Christ-like figure.